Early views on the nature of fossils

'Plastic forces' were believed to be unspecified forces within the Earth that were continually striving to produce organic bodies. The notion that fossils were formed by these 'plastic forces', first put forward by the Persian scholar Avicenna (980-1037 AD), was an outgrowth of the Aristotelian idea of spontaneous generation. Fossils were individuals that had 'failed' at spontaneous generation, or else the 'vital essence' of living things had penetrated rocks and formed objects there which resembled living things. In antiquity and the Middle Ages, a sharp distinction between animate and inanimate things was not recognised. Rocks were thought to be in a sense alive, as they shared with animals and plants the characteristic of growth; for example, miners observed the formation of secondary minerals on the walls of their drives, and minerals were observed to grow around objects placed in springs. The sharp distinction we now recognise between living and non-living things only came about after the invention of the microscope in the 17th century enabled the recognition that living matter is composed of cells.

Neoplatonism was a philosophical outlook that focused on recognising 'hidden affinities' that were to be found between objects in the universe. Under this view, the macrocosm is reflected in the microcosm, and objects sharing 'hidden affinities' might also share the same powers. For example, the stars were seen as guiding the course of human affairs. Cut and polished gems were seen to be like stars because of their brightness and sparkle, and therefore they were imbued with powerful magic. Similarly, under this view fossils were regarded as having a correspondence to living things rather than being the remains of formerly living things. Both Neoplatonism and Aristotelianism had a powerful hold on the minds of 16th century scientists. Until those ideas were discredited, no amount of evidence could persuade scientists that fossils were the remains of once living organisms. The discrediting of those views came from developments in other areas of science; for example, the triumph of the Copernican model of the solar system over that of the Ptolomaic one.

Fossils as relics of the Biblical Flood had a quite independent history from Neoplatonism and Aristotelianism. As early as the 2nd century AD, this idea was supported by Christian writers, who regarded fossils as the remains of once living organisms that were killed and buried during the brief duration of the Flood. It was not recognised that these organisms had existed in the very distant past, nor that different assemblages of fossils succeeded each other in different rock layers.

The decline of the Biblical Flood as an explanation for the occurrence of fossils came about in the 19th century for two major reasons. The first was the rise of the view, championed by Charles Lyell in his influential work Principles of Geology (1830-1836), that Earth history can be interpreted in terms of geological processes operating at the present day, rather than in terms of a series of major catastrophic events, such as the Flood. The second reason was the acceptance that the succession of life through time is due to the process of evolution, as proposed by Charles Darwin in On the Origin of Species (1859), rather than to repeated catastrophic extinctions and the subsequent recreation of life anew.

The true nature of fossils was understood by some of the Greek authors, such as Xenophanes, Pythagoras and Herodotus. Theophrastus (368-284 BC) wrote the first known book on fossils, which is lost, but in another book Peri lithon (On Stones) he referred to it and demonstrated that he had a modern view of what fossils represent.

Leonardo da Vinci (1452-1519) accepted the organic origin of fossils, and on the basis of reasoned arguments, rejected both the Biblical Flood and spontaneous generation as explanations for their presence in rocks. Some of da Vinci's contemporaries, such as Girolamo Fracastoro (1483-1553) had similar views.

Much of the difficulty in interpreting fossils in the past arose from the fact that knowledge of living organisms was limited, so that comparisons with them often could not be made. In addition, in the 16th and 17th centuries, religious support for the account of events in the Bible discouraged dissent from the view that fossils were anything but the remains of organisms drowned in the Flood.

Today creationists still champion the Biblical Flood as an explanation for fossils, but no-one supports 'plastic forces' or Neoplatonism.

References:

Rudwick, M. J. S. 1985. The meaning of fossils. Episodes in the history of palaeontology. University of Chicago Press, 2nd edn.